The invention concerns acceleration engineering, and is especially addressed to induction accelerators. It has application as a commercial-type compact powerful accelerator of charged particles for the formation of relativistic beams of charged particles and for systems of many parallel multi-component beams.
There is known an induction accelerator, which can be used as a device for the formation of singular electronic relativistic beams. Redinato L. “The advanced test accelerator (ATA), a 50-MeV, 10-kA Inductional Linac.” IEEE Trans., NS-30, No 4, pp. 2970–2973, 1983. This device also is called a one-channel linear induction accelerator (OILINAC). The OILINAC is composed of the injector block, the drive source, output system, and a one-channel linear induction acceleration block. Its peculiarity is that the one-channel linear induction acceleration block is made in the form of a sequence of linearly connected acceleration sections. Each of the acceleration sections is made in the form of magnetic inductors, which are enveloped by a conductive screen. The acceleration of the beam is achieved by the effect of longitudinal vortex high-frequency (tens MHz) electric field, which is generated within the acceleration space of the section. The acceleration space is made in the form of a special break in the conductive screen. Thus, the conductive screen shields the outside of the acceleration section (with respect to its inner part) from the penetration of the vortex electric field. This occurs everywhere within the acceleration section, apart from the special break in the conductive screen, which plays a role of the acceleration interval (accelerative space). The acceleration channel in the OILINAC has a linear form. This is the main cause why these systems are called “linear”.
The large linear (longitudinal) dimensions, limited functional potentialities, and a limited range of the current strength of the beam are the basic shortcomings of the OILINAC.
The large dimensions of the OILINAC (e.g. 60–70 m length for the ATA class) are related with its moderate rate of linear acceleration. The typical energy rates of acceleration for the OILINAC are ˜0.7–1.5 MeV/m. For example, in the above-mentioned design of OILINAC [Redinato L. “The advanced test accelerator (ATA), a 50-MeV, 10-kA Inductional Linac.”IEEE Trans., NS-30, No 4, pp 2970–2973, 1983] the averaged value of the acceleration rate is ˜0.75 MeV/m. This means that in the case of the 50-MeV system its total length is ˜70 m. This causes strong complications in overall infrastructure and its accommodation and service (because it needs special accommodation, radiation-protection systems and service, etc.). Consequently, commercial application of OILINAC as a basic construction element for various types of commercial devices becomes economically unsuitable because of their excessive price.
The other shortcoming of the OILINAC is that only one charged particle beam is accelerated on all stages of the acceleration process, i.e., OILINAC is one-channel and one-beam, at the same time. However, a series of practical applications require the formation of charged-particle beams with a multi-component structure, for example, the electron beams for the two-beam superheterodyne free-electron lasers, complex (electron-ion or ion-ion) beams for some technology systems, etc. A direct use of the OILINAC in such situations is impossible, since, as it was mentioned before, they are designed for the formation of exclusively one-energy and one-component relativistic beams of charged particles. This means that the OILINAC possesses limited functional possibilities with respect to potential fields of application.
It is well known that the limitation for the range of beam current strength in the OILINAC exists from the “down” as well as the “upper” sides. The limitation from the “down” side is connected with lower level of its efficiency in the case when the beam current magnitudes are smaller than some critical value. For instance, such critical beam current equals ˜1 kA for most of the modern electronic OILINACs. This happens because the main power losses in OILINAC are related with the losses in the re-magnetization of the magnetic inductor cores. These losses depend mainly on the core material and they do not depend practically on the beam current strength. On the other hand, the useful power is the power which the beam obtains during the acceleration process. This power, in contrast to the first case, depends on the beam current. As it is widely known, the particle efficiency of the acceleration process can be determined as a ratio of the useful power to the total (i.e., sum of the losses and useful) power. This means that the main reason for the efficiency increase is the increase of the beam current. As experience showed, the power of losses became approximately equal to the useful power in the case when (critical) current beam is ˜1 kA. Just owing to this, the modern OILINACs with high level of efficiency are usually characterized by the electron beam current ≧1 kA. However, many practical applications require beams with a lower level of current and, at the same time, high efficiency. The mentioned shortcoming reduces essentially the range of the possible practical OILINAC applications.
The limitation mentioned from the “upper” side is related with an increasing role of the beam instability at an increase of the beam density. Consequently, the formation and the acceleration of electron long tens-kA beams becomes technologically a very complicated problem, and the formation of a few hundreds-ka beams becomes practically impossible.
There is also known an inductional accelerator, which can work as a device for the formation of relativistic beams of charged particles and which is named the multi-channel induction accelerator (MIAC). Two design versions of the MIAC are known including the multi-channel induction linear accelerator (MILINAC) [V. V. Kulish, A. C. Melnyk. Multi-Channel Linear Induction Accelerator, U.S. Pat. No. 6,653,640 B2; issued Nov. 25, 2003.], and the Multi-Channel Induction Undulative Accelerator (MIUNAC) [V. V. Kulish, P. B. Kosel, A. C. Melnyk, N. Kolcio Induction Undulative EH-Accelerator, U.S. Pat. No. 6,433,494 B1, issued Aug. 13, 2001]. The latter is also called the EH-accelerator [V. V. Kulish. Hierarchical Methods. Vol. II. Undulative electromagnetic systems. Kiuwer Academic Publishers, Boston/Dordrecht/London, 2002]. MIAC consists of the injector block, the drive source, the output device, and the multi-channel induction acceleration block. Here the multi-channel acceleration block is made in the form of an aggregate (including that placed parallel with one to other) of one-channel linear induction acceleration blocks. Similarly to the OILINAC, each one-channel linear induction acceleration block is made in the form of a sequence of the linearly connected acceleration sections. In turn, each of the acceleration sections is made in the form of one or few magnetic inductors enveloped by an individual conductive screen.
The MILINAC and MIUNAC design versions distinguish themselves by the form of the partial output devices of the one-channel linear (i.e., partial) induction acceleration blocks. So, the partial output systems in the MILINAC are made in the form of outlets for the accelerated beams. The partial output systems in MILINAC can have also a form of devices that brings together different accelerated beams. It can bring together the beams of the same kind of charged particles (e.g. different-energy beams of electrons or other charged particles) as well as the beams of different kind of particles (electron and ions or positive and negative ions, etc.). This means that particle trajectories of each partial accelerating beam in MILINAC always have a line-like form.
In contrast to the MILINAC at least a part of the partial output systems is made in the form of magnetic turning systems. Each of the turning systems connects the output of one of the one-channel linear induction acceleration blocks with an input of other similar block. Only those inputs, which are connected with injectors, and those outputs, which are destined for coming out the accelerated partial beams, are exceptions from this rule. Thus, each of the acceleration channels in the MIUNAC represents by itself a sequence of linear parts (the partial channels within the one-channel accelerative blocks) and turns for the angle 180° (the part of the channel within a turning system). This gives eventually an undulative-like form of the accelerating charged particle beam. That is why the systems of this class are called the undulative.
Thus, the community of the design variants of the MILINAC and the MIUNAC is characterized in that both contain multi-channel induction acceleration blocks, which are made in the form of an aggregate of one-channel linear induction acceleration blocks (including those oriented parallel one to other). The differences concern the form of the partial output systems of the output block.
Both design versions are not always competitors and each of them has its optimal areas of applications. For instance, the most promising field of the MILINAC utilization is the systems of electron beams with relatively low energy (a few MeV's) and super-high currents (tens-hundreds kA's). Or, it can be used for combined electron-ion or ion-ion high current beams, etc. The main merit of the MIUNAC is its obviously expressed compactness. For example, total length of the OILINAC of the ATA type can be reduced from ˜70 m to ˜13 m in the case, when the MIUNAC design with five turns of the accelerating electron beam is used.
Thus, the multi-channel induction accelerator (MIAC) solves part of the problems that are characteristic for the OILINAC. However, some problems were not solved satisfactorily. One of them, which we consider the main problem, is relatively low MIAC efficiency, especially in the case of the moderate currents of the accelerated beams.